Creating distinct user spaces through user identifiers

ABSTRACT

A method of, and a processing system for, creating distinct user spaces. In a platform originally intended to be a single user platform, for each of a plurality of users, a first application used by the user can be assigned a user identifier (UID) unique to the user and the first application. The first UID can be associated with user data exclusively associated with the user and the first application to create a multi-user platform.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 61/406,328, filed Oct. 25, 2010, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of Technology

The present description generally relates to operating systems and, moreparticularly, to multi-user accounts in operating systems with accessrestrictions.

2. Background

Android™ is a software stack for mobile devices based on the Linux™platform, and currently is developed by Google, Inc. of Mountain View,Calif. Although Linux™ supports multiple users, Android™ is designed tobe a single user platform. In this regard, the Android™ systemeffectively disables the multi-user aspect of the Linux™ kernel byassigning unique user identifiers (UIDs) to each Android™ application.In particular, when an Android™ application reads or writes data, theapplication only can access the data with its unique UID. Thus, such anapplication can only read or modify data that the application itselfcreates. This feature is necessary to prevent potentially unscrupulousapplications from accessing sensitive information generated by otherapplications.

SUMMARY

Arrangements described herein relate to a method of creating distinctuser spaces. The method can include, in a platform originally intendedto be a single user platform, for each of a plurality of users, via aprocessor, assigning to a first application used by the user a useridentifier (UID) unique to the user and the first application andassociating the first UID with user data exclusively associated with theuser and the first application to create a multi-user platform. Themethod further can include assigning to a second application used by theuser a second UID unique to the user and the second application, andassociating the second UID with user data exclusively associated withthe user and the second application.

The method also can include allocating to the user a range of UIDs,wherein the first UID is selected from the range of UIDs. Applicationsused by the user can be assigned the UIDs from the range of UIDs in aserially incrementing manner. When at least one of the applications usedby the user is removed from the single user platform, a correspondingUID can be returned to a pool of available UIDs.

The method further can include allocating for shared usage among theplurality of users a range of UIDs. UIDs can be assigned to applicationsused by the plurality of users, wherein the UIDs are assigned to theapplications in an interleaved manner. Further, a range of UIDs can beallocated for system or administrative use.

The method further can include receiving from a process a request toaccess the user data, the request indicating the first UID exclusivelyunique to the user and the first application. The process can be allowedto access the user data corresponding to the user and the firstapplication.

The method further can include providing user level-servicing using aloop device-based file system to enable the single user platform toaccommodate multiple users. The method also can include providing a newfiling system for the single user platform by writing a list offunctions configured to support and adding an entry into a VirtualFilesystem Switch (VFS) table to enable the single user platform toaccommodate multiple users.

Arrangements described herein also relate to a processing system. Theprocessing system can include a processor configured to, in a platformoriginally intended to be a single user platform, for each of aplurality of users, assign to a first application used by the user afirst user identifier (UID) unique to the user and the first applicationand associate the first UID with user data exclusively associated withthe user and the first application to create a multi-user platform.

The processor further can be configured to assign to a secondapplication used by the user a second UID unique to the user and thesecond application and associate the second UID with user dataexclusively associated with the user and the second application. A rangeof UIDs can be allocated to the user, wherein the first UID is selectedfrom the range of UIDs. The UIDs from the range of UIDs can be assignedto applications used by the user in a serially incrementing manner. Whenat least one of the applications used by the user is removed from thesingle user platform, a corresponding UID can be returned to a pool ofavailable UIDs.

The processor further can be configured to allocate for shared usageamong the plurality of users a range of UIDs. UIDs can be assigned toapplications used by the plurality of users, wherein the UIDs areassigned to the applications in an interleaved manner. Further, a rangeof UIDs can be allocated for system or administrative use.

The processor further can be configured to receive from a process arequest to access the user data, the request indicating the first UIDexclusively unique to the user and the first application and allow theprocess to access the user data corresponding to the user and the firstapplication.

The processor further can be configured to provide user level-servicingusing a loop device-based file system to enable the single user platformto accommodate multiple users. The processor also can be configured toprovide a new filing system for the single user platform by writing alist of functions configured to support and add an entry into a VirtualFilesystem Switch (VFS) table to enable the single user platform toaccommodate multiple users.

Another embodiment can include a computer program product including acomputer-readable storage medium. The computer-readable storage mediumcan include computer-usable program code stored thereon to perform thevarious steps and/or functions disclosed within this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described below in more detail, with reference tothe accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a system in accordance with oneembodiment of the present invention;

FIG. 2 depicts user ranges in accordance with one embodiment of thepresent invention;

FIG. 3 depicts user ranges in accordance with another embodiment of thepresent invention;

FIG. 4 is a flowchart illustrating a method for creating multipleindependent user spaces in accordance with one embodiment of the presentinvention; and

FIG. 5 is a flowchart illustrating a method for creating multipleindependent user spaces in accordance with another embodiment of thepresent invention.

DETAILED DESCRIPTION

While the specification concludes with claims defining features that areregarded as novel, it is believed that the claims will be betterunderstood from a consideration of the description in conjunction withthe drawings. As required, detailed embodiments are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely exemplary and can be embodied in various forms. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representative basis for teaching one skilled in the art to variouslyemploy virtually any appropriately detailed structure. Further, theterms and phrases used herein are not intended to be limiting but ratherto provide an understandable description.

Several definitions that apply throughout this document will now bepresented. The term “current user” is defined as a user of the pluralityof users who currently has access to the programs and/or features of acomputing device. A “user space” is defined as an environment reservedfor a particular user where that user may access various types of dataand perform other computing or communication operations. A “platform” isdefined as an operating environment composed of hardware and/or softwarecomponents that serve as interfaces or specifications for interactionswithin a processing device. A “single user platform” is defined as aplatform that is designed to accommodate a single user space andpossibly an administrator with default control over the platform. A“multiple user platform” is defined as a platform that is designed toaccommodate a more than one user space and possibly an administratorwith default control over the platform. The phrase “originally designedas a single user platform” is defined as a platform that is or wasintended to be a single user platform but that has or will be altered ormodified in some way to accommodate more than one user space. The phrase“collectively store data” is defined as a process in which multipleportions of data are stored across multiple storage elements or across asingle storage element.

The term “computing device” is defined as an electronic deviceconfigured to conduct various operations that manipulate or processdata. A “network” is defined as a collection of two or more componentsin which the components are permitted to at least exchange signals withone another. The word “data” is defined as all forms of information thatare capable of being generated and at least temporarily stored. The word“plurality” means a number that is greater than one.

A “processor” is defined as a component or a group of components thatexecute(s) sets of instructions. A “computer-readable-storage medium” isdefined as a non-transitory storage device that can contain, or store, aprogram for use by or in connection with an instruction executionsystem, apparatus or device. Examples of a computer-readable-storagemedium include, but are not limited to, a hard disk drive (HDD), a solidstate drive (SSD), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), a digital versatile disk (DVD) and a floppydisk. A “program product” is defined as a device comprising acomputer-readable-storage medium having stored thereon computer-usableprogram code.

An “interface” is defined as a component or a group of components thatconnect(s) two or more separate systems or elements such that signalscan be exchanged between or among them. A “directory” is defined as adigital file system structure that includes files and folders and thatorganizes the files and folders into a hierarchical organization. Theword “link” is defined as an object that specifies the location ofanother object. A “symbolic link” is defined as a file system constructthat contains a reference to another file or directory in the form of anabsolute or relative path and that affects pathname resolution.

A “data storage element” is defined as a component or a group ofinterconnected components that are configured to retain data subject toretrieval. The term “non-volatile data storage element” means a datastorage element, such as a computer-readable storage medium, that isconfigured to retain data irrespective of whether the data storageelement is receiving power. The term “volatile data storage element”means a data storage element that requires power during at least someinterval to retain data. An example of volatile data storage is randomaccess memory (RAM).

The term “fixed allocation” is defined as an allocation ofmemory/storage that is assigned prior to the execution of any programsor operations that may utilize the allocation and stays static duringsuch execution of the programs or operations. In contrast, a “dynamicallocation” is defined as an allocation of memory/storage that may ormay not be assigned prior to the execution of any programs or operationsthat may utilize the allocation and is adjustable prior to, during orfollowing such execution of the programs or operations. The terms“encrypt” or “encrypting” are defined as altering or translating data torestrict access to the data, while the terms “decrypt” or “decrypting”are defined as decoding data that has been encrypted. The word“orthogonal” is defined as a state in which two or more pieces ofinformation or data are separated from one another and there is nooverlap between (or among) them.

As noted, the Android™ system relies on user identifiers (UIDs) toisolate application data. All applications or application suites mayhave unique UIDs that are typically generated at installation.Generally, only applications that create a file are able to access thatfile because the Linux file permissions do not allow global access toapplication data. The data normally only can be accessed by a processwith the same UID of the application, and all applications typicallyhave unique UIDs. This data protection mechanism can be extended notonly to isolate data from different applications, but also to segregatedata from the same application created by different users. In general,the association of a unique UID based on, for example, both user andapplication type can be used to prevent users from accessing any databut their own by making all UIDs for a particular user orthogonal to theUIDs for all other users.

Additionally, system file I/O functions can be modified to read andwrite common file names differentiated by UID. For example, if anapplication with UID 0x1234 attempts to write a file foo.txt, themodified file I/O functions can append the UID of the application to thefile name. In this example, the name of the file in the file systemwould be foo.txt-1234, but the application need not read and write tothe file as foo.txt. This would allow applications common to multipleusers to persist data to a data storage element without their datacolliding. Additionally, the modified file I/O read functions can beconfigured to first look for the file name specified with theappropriate suffix. If this file does not exist, then the I/O readfunctions can attempt to find a file with the corresponding file namenot having a suffix. This process can be implemented so thatapplications could find pre-existing system files which would be commonto all users. This process can be implemented for each directory or fileelement in a file path.

FIG. 1 is a block diagram illustrating a system 100 in accordance withone embodiment of the present invention. The system 100 can include aprocessing device 102. The processing device 102 can be a computer(e.g., a desktop computer, a laptop computer, a notebook computer, atablet computer, or the like), a personal digital assistant (PDA), amobile telephone (e.g., a smart phone), an entertainment device, or anyother device suitable for processing data.

The processing device 102 can include a processor 105, which maycomprise, for example, one or more central processing units (CPUs), oneor more digital signal processors (DSPs), one or more applicationspecific integrated circuits (ASICs), one or more programmable logicdevices (PLDs), a plurality of discrete components that can cooperate toprocess data, and/or any other suitable processing device. In anarrangement in which a plurality of such components are provided, thecomponents can be coupled together to perform various processingfunctions as described herein.

In one arrangement, the processing device 102 also can include one ormore input/output (I/O) devices, for example a display 110. In onearrangement, the display 110 can be a touch screen display, though theinvention is not limited in this regard. Another example of an I/Odevice can include an I/O mechanism 115, such as a keyboard, a mouse, orthe like. Of course, the display 110, if built as a touch screendisplay, may serve as the I/O mechanism 115. It should be noted,however, that the processing device 102 is not necessarily limited tothese types of user interface elements, as other forms of suchcomponents may be implemented into the processing device 102.

The I/O devices can be coupled to the processor 105 either directly orthrough intervening I/O controllers. One or more interfaces 140 also canbe coupled to the processor 105 to enable the processing device 102 tobecome coupled to other systems, computer systems, remote printers,and/or remote storage devices through intervening private or publicnetworks. Modems, cable modems, Ethernet cards and communication portsare examples of different types of interfaces 140 that can be used withthe processing device 102. Examples of communication ports include, butare not limited to, serial ports, parallel ports, universal serial bus(USB) ports, IEEE-1394 (FireWire) ports, serial ATA (SATA) ports,external SATA (eSATA) ports, and the like.

The processing device 102 also can include one or more data storageelements 120, 122, which can be used to store various forms of data. Thedata storage elements 120, 122 can be volatile data storage elements ornon-volatile data storage elements. The data storage elements 120 can beintegrated within (permanently or temporarily) the processing device102. As such, the data storage elements 120 can be referred to as localdata storage elements. The data storage elements 120 can be coupled tothe processor 105 either directly or through intervening I/Ocontrollers.

The data storage elements 122 can be communicatively linked to theprocessing device 102 via the communication network 125, via acommunication port, or in any other suitable manner. As such, the datastorage elements 122 can be referred to as remote data storage elements.The communication network 125 can comprise a wide area network (WAN),such as the Internet, a local area network (LAN), a personal areanetwork (PAN) (e.g., Bluetooth®), and/or any other suitablecommunication systems. In this regard, the communication network 125 caninclude wired and/or wireless communication links.

An operating system and/or one or more applications can be stored to oneor more of the data storage elements 120, 122, and executed by theprocessor 105 to implement the methods and processes described herein.Although there are references to Linux™ and Android™ operating systems,it should be noted that the description contained herein is applicableto any operating system, kernel or software platform where support formultiple-user accounts is not provided or available.

In one arrangement, the processing device 102 can also include anencryption engine 130, which can be used to selectively encrypt and/ordecrypt data. Any suitable type and number of encryption and decryptiontechniques can be employed to ensure secure and efficient retrieval ofdata. As another option, the processing device 102 can include anauthentication module 135 for authenticating one or more users of theprocessing device 102. The authentication module 135 can performauthentications on its own or in conjunction with one or more otherelements, as will be described herein.

If desired, the encryption engine 130 and the authentication module 135can be directly and communicatively coupled to the interface 140 forexchanging signals with the communication network 125 or other externalelements. In one arrangement, the encryption engine 130 and theauthentication module 135 can be embodied as application specificdevices coupled to the processor 105 either directly or throughintervening I/O controllers. In another arrangement, the encryptionengine 130 and the authentication module 135 can be embodied asapplications executable by the processor 105. In this regard, theencryption engine 130 and the authentication module 135 can be stored onone or more data storage elements communicatively linked to theprocessor 105.

In accordance with the description herein, the processing device 102 canbe configured to accommodate multiple users. This feature is possibleeven if the processing device 102 is equipped with a platform that wasoriginally intended for use by a single individual. In particular, eachuser can operate the processing device 102 and can generate, store andretrieve data on the processing device 102. This data can be stored onany number or type of the data storage elements 120, 122 including thosethat are communicatively linked to the processing device 102 via thecommunication network 125. In addition, a particular user's data can beprotected from unauthorized access by any of the other users of theprocessing device 102. These processes can be achieved with minimalaffect on the original single user platform of the processing device102.

To configure the processing device, an operating system, for exampleLinux™ or Android™, can be executed by the processor 105. Additionalsoftware and/or applications also may be executed by the processor 105.In one arrangement, user-level servicing using a loop device-based filesystem, such as Filesystem in Userspace (FUSE) or vnode disk (vnd), canbe provided as additional software that executes on top of the operatingsystem to enable the platform of the processing device 102 toaccommodate multiple users, thereby facilitating creation of amulti-user platform. In another arrangement, a FUSE kernel module andFUSE library can be integrated into to the operating system.

In another aspect of the present arrangements, for example within theLinux™ or Android™ operating system, a new filing system for theplatform can be created by writing a list of functions configured tosupport, and an entry can be added into a Virtual Filesystem Switch(VFS) table. A VFS is a kernel data structure that contains an entry foreach type of filing system that the kernel has knowledge. Examples ofsuch filing systems include, but are not limited to, ext3, msdos, procfsand sysfs. Each entry in a VFS can include a list of functions thatimplement file-related system calls (e.g., mount, open, read, write,stat, etc) for a particular type of filing system. The functions in thenew filing system can be configured to call such functions in one ormore other filing systems. In this regard, semantics for the new filesystem can be layered onto an existing file system's data layout (e.g.,ext3 or msdos).

User data can be stored on any suitable number/combination of datastorage elements 120, 122. There are several techniques for realizingisolation of the user data. In particular, a predetermined number ofuser ranges can be generated with each range being associated with allor at least some of the users of a computing device. Referring to FIG.2, an arrangement 200 of numerous user ranges 205-1, 205-2, 205-3, 205-4is shown. As an example, each user range 205 can represent a range ofUIDs that may be allocated to a particular user. In this regard, eachuser range 205 can comprise a portion of the total number of availableUIDs.

In one embodiment, the UID can be an unsigned integer value, and thenumber of available UIDs can depend on the operating system and otherrelevant restrictions. In illustration, some systems support 16 bitUIDs. In such cases, slightly over 65,000 UIDs may be available. Othersystems may support 32 bit UIDs, which may increase the number ofavailable UIDs to over four billion. In any event, the number ofavailable UIDs can be allocated among (or between) the multiple users inany suitable manner.

One specific (but non-limiting) example will be presented. Assume thatthe system supports a 16 bit UID. The UID space can be segmented intosixty-five possible user accounts, with each being assigned one thousandUIDs. User 1 can be allocated the range 0-999 (or 1-999), user 2 can beallocated the range 1,000-1,999 and user 3 can be allocated the range2,000-2,999. The remaining user accounts can be assigned ranges inaccordance with this particular allocation. Whenever a UID is assignedfor an application used by a particular user, the UID can be assignedfrom that particular user's allocated range. Once allocated, the UID canbe unique to the user and the application, at least until the UID isreturned to the pool of available UIDs, for example when the applicationis removed from the platform.

In another example, a range of UIDs can be allocated to a plurality ofusers. Whenever a UID is assigned for an application used by aparticular user, the UID can be assigned from the allocated range.Again, once allocated, the UID can be unique to the user and theapplication, at least until the UID is returned to the pool of availableUIDs, for example when the application is removed from the platform.

There are several other issues to consider in this technique.Specifically, this assignment of ranges can apply to any type of UID.Moreover, any number of user accounts may be created, and an equivalentnumber of UIDs may be assigned to each range. It is understood, however,that the assignment of UIDs is not necessarily limited to anequal-weighted fashion, as some ranges may contain a greater or fewernumber of UIDs in comparison to other ranges. Also, some of the rangesmay be reserved for system or administrative use. In anotherarrangement, one or more common user ranges 210 may be generated. TheUIDs in a common user range 210 may be common to all or at least aplurality of users. Here, an application may be assigned a common UIDfrom this range 210, and these common users may be able to access thedata for the application and can share the data. That is, users are ableto create shared resources by having common UIDs for applications.

In an alternative embodiment, UIDs can be assigned in a seriallyincrementing manner. For example, each application can have a UIDassigned to it at install time, which can be a higher integer value thanthe last application installed by any user. Although not necessarilylimiting, the UIDs can be serially incremented by a value of one. Anexemplary illustration is presented in FIG. 3. There, an arrangement 300is shown in which the first entry relates to a first applicationrestricted to user 1, which has a UID of 1. As an example, a second user(user 2) may install the same application (which can be restricted touser 2), and the UID can be incremented by one to a value of 2. Asanother example, a third user (user 3) can install a second application(which can be restricted to user 3), and the UID can be incremented to avalue of three. Like the previous embodiment, common UIDs can be used toallow for multiple (or even all) users to access and share data andshare, and these UID values can be incremented in a fashion similar tothat described here.

In this way, applications can be assured a unique UID, but it is notnecessary to have a clear segmentation of UIDs. This particular mappingof UIDs can be saved to persistent storage to provide explicitinformation on the UID subsets for the users. This process can alsoallow for an uneven distribution of UIDs among (or between) the users.In addition, the UIDs can be re-mined as time goes on and previouslyinstalled applications are removed. Although the incrementing value ofone is presented, it is understood that the UIDs can be incremented inaccordance with any other suitable value.

In either of the techniques described here, common group identifications(GID) can be used to allow groups of users to access common data. If acommon UID is associated with all users to thereby permit all users toaccess application data, a common GID can allow more than one user butless than all users to access and share application data. Severalexemplary types of data include application data, cache data, media dataand system configuration data. The term “application data” is defined asdata that is associated with programs designed for direct interactionwith an end user. In addition, the term “cache data” is defined as datathat is or will be temporarily stored in a storage mechanism. The term“media data” is defined as data that is associated with the presentationof entertainment to a user. The term “system configuration data” isdefined as data that is used to configure a platform, application, orother software for operation on a device or system. The examplespresented here, however, are not intended to be limiting. Referringagain to FIG. 1, in one particular arrangement, the application data canbe stored in one data storage elements 120, 122, while the cache dataassociated with the users can be stored at a different location of thedata storage elements 120, 122 or on a different data storage element120, 122.

FIG. 4 is a flowchart illustrating a method 400 for creating multipleindependent user spaces in accordance with one embodiment of the presentinvention. The method 400 is not necessarily limited to thechronological order presented in FIG. 4, as these steps can be executedin accordance with any suitable sequence. Also, the method 400 may beadjusted to include other processes or operations not recited here or toremove some of the steps illustrated in FIG. 4.

At step 402, a single user platform can be provided on a processingdevice. At step 404, a range of user identifiers (UIDs) can be allocatedto each of a plurality of UIDs. At step 406, a range of UIDs can beallocated for shared usage among a plurality of users. Step 406 can beperformed in addition to, or in lieu of, step 404. In one arrangement,for example, each user can be allocated a range of UIDs exclusive to therespective users, and another range of UIDs can be allocated for use bya plurality of users. At step 408, a range of UIDs can be allocated forsystem or administrative use.

At step 410, a first UID can be assigned to a first application used bythe user. The first UID can be selected from the range of UIDsexclusively allocated to the user, or selected from the range of UIDsallocated for shared usage among the plurality of users. In eitherarrangement, once assigned, the first UID can be unique to the firstuser and the first application, at least until the first UID is returnedto the pool of UIDs from which the first UID was assigned. UIDs assignedfrom the shared range of UIDs can be assigned to applications used bythe respective users as needed in a serially incrementing manner. Inthis regard, the UIDs can be assigned to applications used by theplurality of users in an interleaved manner. For example, a first UIDcan be assigned to a first application used by a first user, a secondUID can be assigned to an application used by a second user, and a thirdUID can be assigned to a second application used by the first user.

At step 412, a second UID can be assigned to a second application usedby user. The second UID can be selected from the range of UIDs allocatedto the user, or selected from the range of UIDs allocated for sharedusage among the plurality of users. In either arrangement, onceassigned, the second UID can be unique to the first user and the secondapplication, at least until the second UID is returned to the pool ofUIDs from which the second UID was assigned. User identifiers also canbe assigned to applications used by other users as described above.

At step 414, a request to access the user data can be received from aprocess, the request indicating the first UID exclusively unique to theuser and the first application. At step 416, the process can be allowedto access the user data corresponding to the user and the firstapplication. Further, additional requests from the process, or otherprocesses, indicating other UIDs exclusively unique to users andapplications, and such processes can be allowed to access correspondinguser data. At step 418, when at least one of the applications is removedfrom the platform, a corresponding UID can be returned to a pool ofavailable UIDs from which the UID was assigned. Accordingly, the UID canbe made available to be reassigned to the first application or anotherapplication when needed.

FIG. 5 is a flowchart illustrating a method 500 for creating multipleindependent user spaces in accordance with another embodiment of thepresent invention. The method 500 is not necessarily limited to thechronological order presented in FIG. 5, as these steps can be executedin accordance with any suitable sequence. Also, the method 500 may beadjusted to include other processes or operations not recited here or toremove some of the steps illustrated in FIG. 5.

At step 502, a single user platform can be provided on a processingdevice. At step 504, a first UID can be assigned to a first applicationused by the first user. At step 506, additional UIDs can be assigned toadditional applications used by the first user in a seriallyincrementing manner. Further, UIDs can be assigned for shared usageamong a plurality of users and UIDs can be assigned for system oradministrative use in a serially incrementing manner.

At step 508, a request to access the user data can be received from aprocess, the request indicating the first UID exclusively unique to thefirst user and the first application. At step 510, the process can beallowed to access the user data corresponding to the user and the firstapplication. Further, additional requests from the process, or otherprocesses, indicating other UIDs exclusively unique to users andapplications, and such processes can be allowed to access correspondinguser data. At step 512, when at least one of the applications used bythe user is removed from the platform, a corresponding UID can bereturned to a pool of available UIDs.

The flowchart and block diagram in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments. In this regard, each block in the flowchart or blockdiagram may represent a module, segment, or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved.

The systems, components and/or processes described above can be realizedin hardware or a combination of hardware and software and can berealized in a centralized fashion in one processing system or in adistributed fashion where different elements are spread across severalinterconnected processing systems. Any kind of processing system orother apparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware and software can be aprocessing system with computer-usable or computer-readable program codethat, when being loaded and executed, controls the processing systemsuch that it carries out the methods described herein. The systems,components and/or processes also can be embedded in a non-transitorycomputer-readable storage medium, such as a computer-readable storagemedium of a computer program product or other data programs storagedevice, readable by a machine, tangibly embodying a program ofinstructions executable by the machine to perform methods and processesdescribed herein. These elements also can be embedded in a computerprogram product which comprises all the features enabling theimplementation of the methods described herein and, which when loaded ina processing system, is able to carry out these methods.

The terms “computer program,” “software,” “application,” variants and/orcombinations thereof, in the present context, mean any expression, inany language, code or notation, of a set of instructions intended tocause a system having an information processing capability to perform aparticular function either directly or after either or both of thefollowing: a) conversion to another language, code or notation; b)reproduction in a different material form. For example, an applicationcan include, but is not limited to, a script, a subroutine, a function,a procedure, an object method, an object implementation, an executableapplication, an applet, a servlet, a MIDlet, a source code, an objectcode, a shared library/dynamic load library and/or other sequence ofinstructions designed for execution on a processing system.

The terms “a” and “an,” as used herein, are defined as one or more thanone. The term “plurality,” as used herein, is defined as two or morethan two. The term “another,” as used herein, is defined as at least asecond or more. The terms “including” and/or “having,” as used herein,are defined as comprising (i.e. open language).

Moreover, as used herein, ordinal terms (e.g. first, second, third,fourth, fifth, sixth, seventh, eighth, ninth, tenth, and so on)distinguish one message, signal, item, object, device, system,apparatus, step, process, or the like from another message, signal,item, object, device, system, apparatus, step, process, or the like.Thus, an ordinal term used herein need not indicate a specific positionin an ordinal series. For example, a process identified as a “secondprocess” may occur before a process identified as a “first process.”Further, one or more processes may occur between a first process and asecond process.

The present arrangements can be embodied in other forms withoutdeparting from the spirit or essential attributes thereof. Accordingly,reference should be made to the following claims, rather than to theforegoing specification, as indicating the scope of the invention.

What is claimed is:
 1. A method of creating distinct user spaces,comprising: in a platform originally intended to be a single userplatform, for each of a plurality of users: via a processor, assigningto a first application used by the user a first user identifier (UID)unique to the user and the first application; associating the first UIDwith user data exclusively associated with the user and the firstapplication to create a multi-user platform; providing userlevel-servicing using a loop device-based file system to enable thesingle user platform to accommodate multiple users; and allocating tothe user a range of UIDs, wherein the first UID is selected from therange of UIDs.
 2. The method according to claim 1, further comprising:assigning to a second application used by the user a second UID uniqueto the user and the second application; and associating the second UIDwith user data exclusively associated with the user and the secondapplication.
 3. The method of claim 1, further comprising: assigning toapplications used by the user the UIDs from the range of UIDs in aserially incrementing manner.
 4. The method of claim 3, furthercomprising: when at least one of the applications used by the user isremoved from the single user platform, returning a corresponding UID toa pool of available UIDs.
 5. The method of claim 1, further comprising:allocating for shared usage among the plurality of users a range ofUIDs.
 6. The method of claim 5, further comprising: assigning UIDs toapplications used by the plurality of users, wherein the UIDs areassigned to the applications in an interleaved manner.
 7. The method ofclaim 1, further comprising: allocating for system or administrative usea range of UIDs.
 8. The method of claim 1, further comprising: receivingfrom a process a request to access the user data, the request indicatingthe first UID exclusively unique to the user and the first application;and allowing the process to access the user data corresponding to theuser and the first application.
 9. The method of claim 1, furthercomprising: providing a new filing system for the single user platformby writing a list of functions configured to support and adding an entryinto a Virtual Filesystem Switch (VFS) table to enable the single userplatform to accommodate multiple users.
 10. A processing system,comprising: a processor configured to, in a platform originally intendedto be a single user platform, for each of a plurality of users: assignto a first application used by the user a first user identifier (UID)unique to the user and the first application; associate the first UIDwith user data exclusively associated with the user and the firstapplication to create a multi-user platform; provide userlevel-servicing using a loop device-based file system to enable thesingle user platform to accommodate multiple users; and allocate to theuser a range of UIDs, wherein the first UID is selected from the rangeof UIDs.
 11. The processing system of claim 10, wherein the processorfurther is configured to: assign to a second application used by theuser a second UID unique to the user and the second application; andassociate the second UID with user data exclusively associated with theuser and the second application.
 12. The processing system of claim 10,wherein the processor further is configured to: assign to applicationsused by the user the UIDs from the range of UIDs in a seriallyincrementing manner.
 13. The processing system of claim 12, wherein theprocessor further is configured to: when at least one of theapplications used by the user is removed from the single user platform,return a corresponding UID to a pool of available UIDs.
 14. Theprocessing system of claim 10, wherein the processor further isconfigured to: allocate for shared usage among the plurality of users arange of UIDs.
 15. The processing system of claim 14, wherein theprocessor further is configured to: assign UIDs to applications used bythe plurality of users, wherein the UIDs are assigned to theapplications in an interleaved manner.
 16. The processing system ofclaim 10, wherein the processor further is configured to: allocate forsystem or administrative use a range of UIDs.
 17. The processing systemof claim 10, wherein the processor further is configured to: receivefrom a process a request to access the user data, the request indicatingthe first UID exclusively unique to the user and the first application;and allow the process to access the user data corresponding to the userand the first application.
 18. The processing system of claim 10,wherein the processor further is configured to: provide a new filingsystem for the single user platform by writing a list of functionsconfigured to support and add an entry into a Virtual Filesystem Switch(VFS) table to enable the single user platform to accommodate multipleusers.
 19. A computer program product comprising: a computer-readablestorage medium comprising computer-usable program code stored thereonthat creates distinct user spaces, the computer-readable storage mediumcomprising: computer-usable program code configured to, in a platformoriginally intended to be a single user platform, for each of aplurality of users: assign to a first application used by the user afirst user identifier (UID) unique to the user and the firstapplication; associate the first UID with user data exclusivelyassociated with the user and the first application to create amulti-user platform; provide user level-servicing using a loopdevice-based file system to enable the single user platform toaccommodate multiple users; and allocate to the user a range of UIDs,wherein the first UID is selected from the range of UIDs.
 20. Thecomputer program product of claim 19, the computer-readable storagemedium further comprising: computer-usable program code configured toassign to a second application used by the user a second UID unique tothe user and the second application; and computer-usable program codeconfigured to associate the second UID with user data exclusivelyassociated with the user and the second application.
 21. The computerprogram product of claim of claim 19, the computer-readable storagemedium further comprising computer-usable program code configured toassign to the applications used by the user the UIDs from the range ofUIDs in a serially incrementing manner.
 22. The computer program productof claim of claim 21, the computer-readable storage medium furthercomprising computer-usable program code configured to, when at least oneof the applications used by the user is removed from the single userplatform, return a corresponding UID to a pool of available UIDs. 23.The computer program product of claim 19, the computer-readable storagemedium further comprising computer-usable program code configured toallocate for shared usage among the plurality of users a range of UIDs.24. The computer program product of claim 23, the computer-readablestorage medium further comprising computer-usable program codeconfigured to assign UIDs to applications used by the plurality ofusers, wherein the UIDs are assigned to the applications in aninterleaved manner.
 25. The computer program product of claim 19, thecomputer-readable storage medium further comprising computer-usableprogram code configured to allocate for system or administrative use arange of UIDs.
 26. The computer program product of claim 19, thecomputer-readable storage medium further comprising: computer-usableprogram code configured to receive from a process a request to accessthe user data, the request indicating the first UID exclusively uniqueto the user and the first application; and computer-usable program codeconfigured to allow the process to access the user data corresponding tothe user and the first application.
 27. The computer program product ofclaim 19, the computer-readable storage medium further comprising:computer-usable program code configured to provide a new filing systemfor the single user platform by writing a list of functions configuredto support and adding an entry into a Virtual Filesystem Switch (VFS)table to enable the single user platform to accommodate multiple users.